The invention concerns a material mass for the removal, through chemical sorption of oxygen, impurities from a gas to be purified.
Such a material mass is generally described in U.S. Pat. No. 3,852,406 ("Krauss Patent"). It can be employed with great effectiveness especially for the removal of oxygen which is present in minute traces, as for example in the preparation of high-purity gases and test gases. The operation of removing oxygen which is present in minute amounts is finding increased application in the semi-conductor industry, in which reactive hydrides are employed as process gases. Here, the purity of the process chemicals being used is of decisive significance for the yield effect which it may have on operating capacity.
The presence of oxygen in minute amounts effects, in a number of procedural stages, as e.g. in CVD (Chemical Vapor Deposition) procedures, a drastic deterioration of the electrical properties of the semi-conductor structural units, by increasing the oxygen defect density in the semi-conductor material. In the removal of the traces of oxygen found in inert cleansing and carrier gases, which are employed in large amounts in the structural member of semi-conductor manufacture, the material masses presented by the Krauss Patent has given an excellent accounting of itself. Yet, in the case of the group of reactive process gases used in semi-conductor manufacture, such as, e.g., silane, disilane, dichlorsilane, diborane, arsine, in addition to certain chelate or chelate compounds such as trimethylgallium, trimethylaluminum, trimethylindium, and corresponding ethyl compounds, no possibilities have existed up to now of a secondary cleansing in situ, i.e., at the place of consumption. The hydrides capable of reaction will react, as is known, exothermically with free hydrodroxyl groups of the oxidic carrier material within the batch. In a second, parallel-occurring reaction, the active metallic centers of the mass are reduced to a low stage of oxidation which is as yet undefined. The possibility of secondary cleansing in situ for this group of process gases and chelate compounds would be desirable inasmuch as these components are, as a general rule, centrally produced, and arrive at the actual place of consumption by way of extended supply channels. With this state of affairs, a certain contamination of the reactive process gases at one's disposal cannot be avoided.